This invention generally relates to systems, methods and computer program code storing and processing data, in particular large volumes of data captured by monitoring digital mobile communications networks such as digital mobile phone networks.
FIG. 1 shows a simplified block diagram of a generic mobile communications network 100 such as a CDMA (code division multiple access), UMTS (universal mobile telecommunications system) or GPRS (general packet radio service) network. The terminology applied herein is not meant to imply limitation to any particular type of network.
Referring to FIG. 1, the network has a plurality of fixed base stations 102A-C referred to as base transceiver stations (BTS) or node B's each coupled to a respective base station subsystem 104A, B comprising a base station controller (BSC) or radio network controller (RNC) and a data packet control function (PCF) or packet control unit (PCU). Voice traffic is passed via a circuit switched connection to one or more voice switches 108 such as a Mobile services Switching Centre (MSC) and data traffic is passed via a packet switch connection to one or more packet switches 114 such as a PDSN (packet data switch node) or SGSN (serving GPRS support node). The voice switch(s) 108 connect via other core network elements 110 to a voice phone network such as PSTN (public switched telephone network) and the packet switch(s) 114 connect via further core network elements 116 to the Internet 118. Mobile stations 106A, B attach to one or more of the base stations.
The techniques we describe herein are useful for a range of networks including GSM (Global System for Mobile Communications) and GPRS but are especially helpful when storing and processing data captured from 3G mobile communications networks such as CDMA and UMTS networks. The terminology used for the different network elements varies depending upon the type of network and in this specification the use of particular terminology, for convenience, does not imply limitation to any specific type of network.
Generically the latest generation of telecommunications networks (3GI third generation) are encompassed by the International Mobile Telecommunications IMT-2000 standard which encompasses wideband CDMA (WCDMA) direct spread FDD (frequency division duplex) systems in Europe and Japan, CDMA2000 multicarrier FDD for the USA, and TD-SCDMA (time division duplex synchronous CDMA) for China. Further details of each of these specifications may be obtained by reference to the appropriate standards, which are the standards produced by the 3rd Generation Partnership Project (3GPP, 3GPP2, hereby incorporated by reference. Examples of these, incorporated by reference, include TS23.101 (general UMTS architecture), TS25.101 (radio transmission and reception), TS23.060 (GPRS—General Packet Radio Service), TS25.433 (NBAP—Node B Application Part); TS25.331 (RRC—Radio Resource Control); TS24.008 (MM—Mobility Management); TS24.008 (CC—Call Control); TS25.322 (RLK—Radio Link Control); TS25.321 (MAC—Medium Access Control).
Referring again to FIG. 1, a large number of interfaces are defined of which some are shown, in particular the Abis (CDMA2000) or Iub (UMTS) interface 103 between a base station and a base station subsystem, and the Aquater (CDMA) or Iu (UMTS) interface 105 between a PCF/PCU and a packet switch 114. In a CDMA2000 system the Aquater interface comprises an A10 interface used to provide a path for user traffic between a PCF and a PDSN, and an A11 interface used to provide a signalling connection between a PCF and a PDSN for packet data services. Other interfaces in a CDMA2000 system include the Ater interface comprising A3 (user traffic and signalling) and A7 (signalling) for handoff (in Europe called handover) between base stations, and the A8 (user traffic) and A9 (signalling) interfaces between a BSC and PCF for packet data services. The AS interface provide a path for user traffic for circuit-oriented data calls between a source base station (BS) and the MSC.
Various techniques are known for capturing data relating to the operation of a mobile communications network, depending upon the level at which the data is obtained. Generally mobile communication networks include an Operation and Maintenance Centre (OMC) (not shown in FIG. 1) which collects statistics from network infrastructure elements such as base stations and switches and compiles these into a database. This provides network operators with a high level view of the network performance and, for example, an OMC typically includes counters for every dropped call split out by cells and time. However, because OMC data comprises only high level statistics it is of limited usefulness in trouble shooting. For example OMC data cannot provide information relating to an individual communication session. Other high level data on how a network is performing can be obtained from call detail records (CDRs) and SS7 (signalling system number 7) data. At a lower level some diagnostic logs are available from individual items of equipment such as base station controller.
It is also known to tap a link or interface between infrastructure elements (either logical or physical) using a protocol analyser or IP (internet protocol) sniffer to record all the data flowing on such a link or across such an interface as a trace or log file. Such file can contain all the messaging between the two elements connected by the tapped link, for example all the messaging between a base station subsystem and a switch. However, there is a need for tools to extract useful information from such captured data.
At a still lower level a network may be tested by means of a simulated user “drive test” in which a mobile station is caused to establish calls in regular patterns to test a network. During these test calls a portable computer attached to the mobile stations gathers diagnostic information from the mobile, generally including air interface messaging, which is stored for later analysis. Alternatively diagnostic information may be incorporated into the test traffic stream so that this can be captured, together with associated signalling, from an interface within the network, as described further in the applicant's International patent application WO 03/047280, the contents of which are hereby incorporated by reference.
There is a need for improved diagnostic tools for mobile communications networks. For example, there is a need for techniques for handling and providing useful information from the vast quantities of data which may be captured at an interface of a mobile phone network.
In particular there is a need for techniques which facilitate the monitoring of a plurality of communications sessions in parallel, for example monitoring a plurality of simultaneous voice and/data calls and parameters associated therewith to determine how a particular network entity such as a handset or base station controller, or a set of such entities is/are behaving, and whether or not the entities or more generally the network is operating correctly and/or in the most efficient manner. As previously mentioned high level statistical data of the type captured by an OMC is of little use in this task, whilst drive test systems are, broadly speaking, restricted to testing the behaviour of the network in relation to a single mobile device. However a stream of messages captured from a point within the network, typically one of the many interfaces defined in the network specifications, can provide information about the operation of a plurality of network entities, although to make good use of such information special techniques are desirable. For example in a UMTS mobile phone network special techniques may be needed to identify messages relating to a particular communications session within a stream of messages, for example to track a particular voice/data call, and such techniques are described in UK patent application no. 0322979.6 filed by the applicant on 1 Oct. 2003, the contents of which are hereby incorporated in their entirety by reference. Likewise specialised data mining techniques are described in the applicant's PCT application GB 2004/000262 filed 27 Jan. 2004, the contents of which are again hereby incorporated in their entirety by reference.
The applicant's earlier patent applications described techniques useful for call tracking and network monitoring in mobile communications systems but further improvements are desirable, in particular in connection with the processing time needed to handle many thousands of messages, preferably on a computer such as a laptop, and in the handling of certain specific technical problems relating to processing and obtaining information and/or statistics of dropped calls, timeouts, handovers, throughput and the like. Broadly speaking a common feature of these events is that one does not know that the event occurred until sometime afterwards, for example when a timeout indicates an earlier failure or when messages appearing in a steam turn out to be related to a subsequent handover of a call to, say, a particular base station (in UMTS this may be complicated by soft handover).